Objective: 

The objective of this study was to analyse the effects of anaerobic threshold (AT) on respiratory patterns and regulation of ventilation (VE) during incremental exercise test.

Methods: 

Ten sedentary male subjects (19.7±0.2 yr, 68.3±2.3 kg) were performed an incremental exercise test (15 W/min) until the limit of tolerance using an electromagnetically-braked cycle ergometer. Before the study, each subject gave signed written informed contents which were approved by the local ethical committee. Respiratory patterns (total time, Ttot, inspiratory time, Ti and expiratory time, Te) and VE were measured using spirometry. The relationships between VE and work rate were used to estimate AT. A paired t- test was used to evaluate values (P<0.05).

Results: 

Ti/Ttot and Te/Ttot did not change below the AT. However, above the AT, Ti/Ttot increased 10% (p=0.01) but Te/Ttot decreased 7% (p=0.01). VE increased 19.9±1.0 L/min (warm-up) to 43.0±1.7 L/min (at the AT) and 125.8±6.3 L/min (at the maximal exercise). Below AT, VE increased due to the increase (74%) in tidal volume (VT). However, above AT, VE increased with closely increasing breathing frequency (115%). VT/Ti was 0.767±0.05 L/s at warm-up and 1.762±0.1 L/s at the AT (139% increase), and 4.440±0.1 L/s at maximal exercise (506% increase).

Conclusions: 

The aerobic and anaerobic regions of incremental exercise test have a marked influence on respiratory patterns. The end productions of anaerobic metabolism above the AT, mainly affects Te and breathing frequency. The widely evaluation of aerobic and anaerobic regions on respiratory patterns during exercise is essential to determine its role in impaired exercise tolerance, especially in patient with respiratory system problems.